1.3.2 Antigen Recognition in the Adaptive Immune System Flashcards
What are some basic characteristics of BCRs and TCRs?
Each BCR/TCR recognizes one antigen with high affinity and ALL BCRs/TCRs on a given cell are identical
What is an antigen?
Any substance that can bind specifically to an antibody or TCR
Immunogen?
An antigen capable of eliciting an immune response
What is an epitope/antigenic determinant?
Portion of the antigen that binds to the Ab or TCR
What does the term monoclonal mean?
A lymphocyte mediated immune response in which all involved lymphocytes are derived from a single clone
What does the term polyclonal mean?
a lymphocyte mediated immune response in which all involved are derived from multiple clones
What is cross-reactivity?
The binding of an antigen by an antibody or TCR specific for another antigen
What is an example of cross-reactivity?
Ex. Antibodies against Streptococcal M protein can cross react with myocardial antigens
Dimer – alpha/beta – mostly in lymphoid tissue, Transmembrane proteins, One ligand-binding region are characteristics of a TCR or BCR?
TCR
Presented on MHC and is primarily peptides and can be anywhere within the protein and must be sequential amino acids are characteristics of the antigens presented to TCRs or BCRs?
TCRs
Dimer of dimers – two heavy and two light chains, transmembrane or soluble, two ligand binding regions are characteristic of a TCR or BCR?
BCR
Native antigen which can be proteins, lipids, polysaccharides, or DNA and must be on the surface of Ag and can be sequential residues or residue brought together by conformation are characteristics of the antigens presented to TCRs or BCRs?
BCR
What is a super-antigen?
Microbial antigen that cross-link TCR and MHC independently of antigen specificity, outside of the peptide binding groove
What can a super antigen result in?
This leads to poly-clonal T cell responses which can lead to a cytokine storm
What are some possible sources of super antigens?
Staphylococcus, streptococcus, mycoplasma, Epstein Barr virus, and Rabies
Determination of whether a BCR is soluble or membrane bound is determined by what?
splicing of the mRNA
What are the two chains of the BCR?
Heavy and light chain
What are the two regions of the heavy and light chain?
Variable and constant regions
The complementary determining region is also known as what?
The hypervariability region
The Fab region is?
The Ag-binding fragment
The FC region is?
Crystallizable
What provides the structure and flexibility of the hinge region?
Proline-rich regions provide the structure while the flexibility is provided by high levels of glycine
What is the importance of the flexibility of BCRs?
The hinge region can flex to allow binding Ag in different conformations. Binding Ag also induces conformation changes in the constant region enabling binding to complement or Fc receptors
What is the biggest antibody isotype?
IgM - Pentamer
What antibodies are rare in sera?
IgD and IgE